There are various ways of determining position both linearly and angularly, and they are covered in this invention. This determination is not as simple as taking a ruler and measuring, because some of the distances involved are very small, relating to multiples of angstroms rather than inches or yards or miles. The invention, in its linear aspects, is primarily for determining such very short distances.
The determination of angles is a matter that also involves small angles but can involve somewhat larger ones. The invention is useful in terms of small fractions of a radian as well as for larger angles.